The human dorsal anterior cingulate cortex (dACC) has been implicated in cognitive processes that have been proposed to play a role in integrating contextual information needed to select or modify appropriate motor responses. In humans, however, there has been little direct evidence tying the dACC to the integration of contextual information and behavioral response. We used single-neuron recordings from human subjects to evaluate the role of the dACC in reward-based decision making. Subjects undergoing planned surgical cingulotomy performed a task where they were instructed to make specific movements in response to changing monetary rewards. In many neurons, activity increased in response to a diminished reward, and was also predictive of the movement ultimately made. After dACC ablation, subjects made selectively more errors when they were required to change movement based on reward reduction. These findings suggest that the dACC in humans plays an important role in linking reward-related information with alternative actions.